Preparation method and application of novel silicon-carbon composite material based on graphite core

Abstract

The invention relates to a preparation method and application of a novel silicon-carbon composite material based on a graphite core, and belongs to the technical field of lithium ion battery negative electrode materials. The preparation method specifically comprises the following steps: S1, uniformly mixing graphite and a coating agent, and drying; s2, placing in a carbonization furnace, heating for pre-carbonization to obtain a graphite particle inner core-carbon shell structure, adding a pore forming agent, heating and cooling to obtain a first composite material; s3, carbonizing the first composite material in a carbonization furnace to obtain a carrier; s4, weighing a carrier, putting the carrier into a fluidized bed, introducing nitrogen, raising the temperature, introducing monosilane in sections, raising the temperature, introducing acetylene, and naturally cooling to room temperature to obtain a primary carbon-coated negative electrode material; s5, adding the solid electrolyte into the polymer aqueous solution, and uniformly dispersing to obtain slurry; and S6, spraying and coating the slurry on the surface of the primary carbon-coated negative electrode material, and then drying to obtain the novel silicon-carbon composite material based on the graphite core. According to the material, the high-temperature, fast-charge and cycle stability of the material can be improved.

Description

Technical Field

[0001] This invention relates to a method for preparing and applying a novel silicon-carbon composite material based on a graphite core, belonging to the field of lithium-ion battery anode material technology. Background Technology

[0002] In recent years, lithium-ion batteries have been widely used in portable electronic devices and electric vehicles. With the rapid development of the new energy industry, the market has placed higher demands on the energy density and cycle life of lithium-ion batteries. Traditional graphite anode materials, with a theoretical specific capacity of only 372 mAh / g, have gradually shown limitations in the face of the increasingly stringent market demands for high-energy-density batteries. Silicon materials, with their ultra-high theoretical specific capacity of up to 4200 mAh / g, have demonstrated enormous potential as next-generation lithium-ion battery anode materials and have become a hot research topic in recent years.

[0003] The invention patent with announcement number CN120015805A discloses a polymer-coated silicon-carbon material and its preparation method, application, and battery. The preparation method includes the following steps: (1) reacting a mixture of 1,3-dioxolane, lithium salt, and silicon source at 30-60°C for 24-96 hours to obtain a polymer-coated silicon material; the lithium salt includes lithium tetrafluoroborate and lithium fluoride; the mass ratio of the 1,3-dioxolane to the lithium salt is (2-10):1; (2) mixing the polymer-coated silicon material with a carbon source to obtain the polymer-coated silicon-carbon material. Although this patent coats the surface of nano-silicon particles with polymer to improve the rate performance of the material, it cannot effectively alleviate the volume expansion of silicon particles.

[0004] Invention patent CN120565599 discloses a negative electrode material, its preparation method, and its application. The negative electrode material includes a porous matrix and a coating layer disposed on the porous matrix. The porous matrix includes a solid electrolyte, and the coating layer includes a silicon material. The specific surface area of ​​the porous matrix is ​​1 m². 2 / g-5m 2 / g. The negative electrode material provided in this application includes a silicon coating layer, which can improve the energy density of the battery. The porous matrix includes an oxide solid electrolyte, which can increase the number of ion conduction pathways, alleviate the volume expansion of the negative electrode material, improve the ionic conductivity and structural stability of the negative electrode material, and improve the cycle safety of the battery. However, the single-layer coating design makes the carbon layer prone to cracking due to the volume expansion of silicon particles during subsequent cycles. At the same time, adding too much solid electrolyte to the negative electrode material will reduce the dispersibility of the electrode slurry and decrease the overall performance of the negative electrode sheet.

[0005] There are also some problems that need to be solved in the use of silicon anode materials. During the charging and discharging process, silicon anodes will undergo a very significant volume expansion phenomenon, with a volume expansion rate of more than 300%. Such a large volume change will lead to a series of serious consequences: (1) the internal structure of the electrode suffers irreversible damage, causing the active material to fall off the electrode surface and gradually pulverize; (2) the solid electrolyte interphase (SEI) film is also difficult to maintain a stable state due to the stress of volume expansion, resulting in a sharp decline in the cycle performance of the battery and a significant increase in internal resistance; (3) silicon itself is a semiconductor material, and its conductivity needs to be improved.

[0006] To address the aforementioned problems with silicon anodes, the main solution currently involves silicon composites, specifically combining silicon with highly conductive carbon materials. This improves the conductivity of the materials and buffers the volume expansion of silicon, enabling the silicon anode material to exhibit high energy density and stable cycle performance. Among the various processes for preparing silicon-carbon composite materials, chemical vapor deposition (CVD) has become the most commonly used method due to its unique advantages. Subsequently, based on specific capacity requirements, the CVD silicon-carbon composite material and graphite need to be mixed in a specific ratio to obtain the desired CVD silicon-carbon / graphite anode material. In this mixing method, because graphite has superior ionic and electronic conductivity compared to the CVD silicon-carbon composite material, this difference affects the overall rate capability and cycle performance of the battery material. Therefore, developing a novel silicon-carbon anode material structure to overcome these problems has become a pressing technical challenge for those skilled in the art. Summary of the Invention

[0007] The primary technical objective of this invention is to address the problems in the prior art by providing a method for preparing a novel silicon-carbon composite material based on a graphite core.

[0008] The second technical objective of this invention is to provide an application of a novel silicon-carbon composite material based on a graphite core.

[0009] The first technical objective of this invention is achieved through the following technical solution: A method for preparing a novel silicon-carbon composite material based on a graphite core includes the following steps: S1. Graphite and coating agent are mixed evenly and dried to obtain the first mixture; S2. The first mixture is placed in a carbonization furnace and pre-carbonized under a nitrogen atmosphere to obtain a graphite particle core-carbon shell structure. A pore-forming agent is added and the mixture is heated to activate and form pores. The mixture is then cooled to room temperature under a nitrogen atmosphere to obtain a composite material based on a graphite particle core and a porous carbon shell, wherein the microporosity is 40-85%, the mesoporosity is 10-30%, and the mesopore size is 2-5 nm. S3. The above-mentioned composite material based on graphite particle core and porous carbon shell is placed in a carbonization furnace for carbonization to obtain a carrier. S4. Weigh a certain mass of the carrier and put it into the fluidized bed, introduce nitrogen gas, raise the temperature, introduce silane in stages, stop introducing silane after the deposition is completed, raise the temperature again, introduce acetylene, stop introducing acetylene after the coating is completed, and cool naturally to room temperature to obtain a CVD silicon-carbon / graphite anode material with one carbon coating. S5. Add the solid electrolyte to the polymer aqueous solution and disperse it evenly to obtain a slurry; S6. Spray the slurry onto the surface of the CVD silicon-carbon / graphite anode material with primary carbon coating prepared above, and then dry it to obtain a novel silicon-carbon composite material based on a graphite core.

[0010] This invention uses graphite as a substrate, coating porous carbon onto the graphite surface. By designing the micro-mesopore ratio of the porous carbon and depositing silicon nanoparticles in a stepwise manner, a composite material is obtained. Subsequently, a carbon layer and a polymer composite solid electrolyte layer are sequentially coated on the silicon material with the above structure to obtain a novel silicon-carbon composite material with a graphite core. This composite material has excellent characteristics such as low expansion, long cycle life, and fast charging. Compared with the traditional physical mixing of graphite and CVD silicon-carbon, this material shows broad application prospects in the field of lithium-ion batteries.

[0011] The silicon nanoparticles are deposited through a stepwise deposition process using silane gas introduced in stages. In the early stages of silicon infiltration, a low concentration of silane gas can appropriately increase the adsorption capacity of mesopores for silane, and also fill some silicon within the mesopores, preventing physical barriers to silicon material and thus hindering lithium-ion diffusion. In the later stages, a high concentration accelerates the pore closure, reducing the specific surface area of ​​the material and simultaneously hindering silicon grain growth. Medium to low concentrations of acetylene readily form a uniform, dense, and continuous carbon coating layer on the material surface, increasing conductivity and acting as a buffer layer for silicon volume expansion.

[0012] A porous polymer composite solid electrolyte layer is coated outside the carbon separator layer. This effectively buffers the volume changes of silicon during charging and discharging, reducing electrode structure damage and SEI film rupture caused by expansion, thereby improving the cycle stability of the battery. Simultaneously, it enhances the conductivity of the electrodes, provides uniform lithium-ion diffusion channels, reduces lithium-ion diffusion resistance, and improves rate performance and fast-charging performance. This electrolyte layer further reduces the contact between the negative electrode and the electrolyte, minimizing side reactions, improving initial coulombic efficiency, and extending the battery's cycle life. In addition, this porous polymer composite solid electrolyte layer also improves the stability of silicon-carbon materials at high temperatures.

[0013] Preferably, a method for preparing a novel silicon-carbon composite material based on a graphite core includes the following steps: S1. Mix graphite and coating agent evenly and dry, wherein the coating agent accounts for 60% of the total mass of graphite particles and coating agent; S2. The mixture is placed in a carbonization furnace and pre-carbonized at 600℃ for 2 hours under a nitrogen atmosphere at a rate of 2℃ / min to obtain a graphite particle core-carbon shell structure. A pore-forming agent is added according to calculations, and the mixture is kept at 700~950℃ for 1~3 hours to activate and form pores. The mixture is then cooled to room temperature under a nitrogen atmosphere to obtain a composite material based on a graphite particle core and a porous carbon shell, wherein the microporosity is 40-85%, the mesoporosity is 10-30%, and the mesopore size is 2-5nm. S3. The above composite material based on graphite particle core and porous carbon shell is placed in a carbonization furnace and carbonized at 500~700℃ for 1~3h to obtain a carrier; S4. Weigh a certain mass of the carrier and put it into the fluidized bed. Introduce nitrogen gas and heat it to 450~490℃ at a rate of 5℃ / min. Introduce a certain amount of silane in stages (the density is calculated as 1.44g / L, and the decomposition rate of silane in this temperature range is calculated as 90%). After the deposition is completed, stop introducing silane. Heat it to 570~600℃ at a rate of 5℃ / min. Introduce acetylene according to the coating amount of 2~5%. After the coating is completed, stop introducing acetylene and let it cool naturally to room temperature to obtain a single carbon-coated CVD silicon-carbon / graphite anode material. S5. Add the solid electrolyte to the polymer aqueous solution and disperse it evenly to obtain a slurry; S6. Spray the slurry onto the surface of the CVD silicon-carbon / graphite anode material with primary carbon coating prepared above, and then dry it to obtain a novel silicon-carbon composite material based on a graphite core.

[0014] As a preferred embodiment of the above technical solution, in step S1, the graphite D50 is 8±1μm; the coating agent includes phenolic resin, asphalt or coconut shell-based biomass carbon; wherein the coating agent accounts for 60% of the total mass of the graphite particles and the coating agent.

[0015] In this invention, phenolic resin, asphalt, and coconut shell biomass (coating agent) were subjected to thermogravimetric analysis in a nitrogen atmosphere. The heating rate of the thermogravimetric analysis was 1℃ / min, thereby obtaining the carbonization mass yield of phenolic resin or asphalt at different temperatures. Since the weight loss rate of the phenolic resin, asphalt, and coconut shell biomass used slows down significantly after the temperature reaches 600℃, the carbonization temperature of phenolic resin and asphalt was set at 600℃, and the holding time was 2h. Under these conditions, the carbonization mass yields of phenolic resin, asphalt, and coconut shell were 52%, 49%, and 43%, respectively.

[0016] Phenolic resin, asphalt, or coconut shell-based biomass carbon can be physically mixed and adhered to the graphite surface, followed by high-temperature carbonization to form a carbon coating layer on the graphite surface. A pore-forming agent creates pores in the carbon layer. Since activators such as water vapor, carbon dioxide, and potassium hydroxide are difficult to use to create pores in graphite particles, the pores are all distributed within the carbon shell. The pore size distribution can be controlled by adjusting the concentration and type of the pore-forming agent, as well as the etching time.

[0017] The presence of micropores provides high-energy sites and high specific surface area, and has a strong adsorption capacity for silane molecules. Silane can decompose into nano-silicon at 460~490℃. The pores provide an effective buffer space for the expansion of nano-silicon. Subsequently, a dense and uniform carbon layer is deposited on the outer surface of the material through acetylene decomposition, which not only improves the conductivity of the composite material, but also provides a buffer layer for the expansion of nano-silicon.

[0018] As a preferred embodiment of the above technical solution, in step S2, the pore-forming agent is one or two of water vapor, carbon dioxide, or potassium hydroxide; the pre-carbonization temperature is 300-500℃, and the pre-carbonization time is 2-3 hours; the activation temperature is 700-950℃, and the activation time is 3-8 hours; the specific surface area of ​​the composite material is 1400-2100 m². 2 / g, total pore volume is 0.74-1.1cm³ 3 / g, microporosity 40-85%, mesoporosity 10-30%, average pore size 1.8-2.4nm.

[0019] As a preferred embodiment of the above technical solution, in step S3, the carbonization temperature is 500~700℃ and the carbonization time is 1~3h.

[0020] As a preferred embodiment of the above technical solution, in step S4, the silane deposition temperature is 460~490℃, the total amount of nitrogen carrier gas and silane gas introduced is 15L / min, and the concentration of silane introduced in stages is 5~20%; the primary coating temperature is 570~600℃, the total amount of nitrogen carrier gas and acetylene gas introduced is 15L / min, and the acetylene concentration introduced is 5~15% based on a coating amount of 2~5%.

[0021] As a preferred embodiment of the above technical solution, in step S5, the solid electrolyte is selected from at least one of lithium lanthanum titanium oxide, lithium aluminum titanium phosphate, lithium aluminum germanium phosphate, lithium lanthanum zirconium oxide, lithium germanium phosphorus sulfide, lithium phosphorus oxy nitrogen, or lithium phosphate; the polymer is selected from at least one of phenolic resin, acrylamide, polyethylene, polystyrene, polyvinyl alcohol, polyvinyl chloride, polyether, polyester, polyamide, polyurethane, polysulfide rubber, polymethyl methacrylate, or styrene-butadiene rubber; the solid content of the polymer aqueous solution is 1-3%; the solid content of the slurry is 30%-45%; the mass ratio of the polymer to the solid electrolyte is (10%-85%):(90%-15%), and the sum of the masses of the polymer and the solid electrolyte is 100%.

[0022] As a preferred embodiment of the above technical solution, in step S6, the spray temperature is 90℃~100℃; the drying temperature is 150℃~300℃, and the drying time is 0.5h~4h.

[0023] The second technical objective of this invention is achieved through the following technical solution: Applications of a novel silicon-carbon composite material based on a graphite core include its use as a negative electrode material in the fabrication of lithium-ion batteries.

[0024] In summary, the beneficial effects of this invention are as follows: 1. This technical solution prepares a novel silicon-carbon composite material by coating CVD silicon-carbon material onto the surface of graphite particles, and then sequentially coating a carbon layer and a polymer composite solid electrolyte layer on the outside of the silicon-carbon material with a specific structure. This material can effectively suppress the volume change of silicon particles during charging and discharging, prevent silicon particles from breaking and falling off during cycling, and maintain the integrity of the electrode structure. 2. This technical solution controls the ratio of micropores to mesopores by designing a physical and chemical pore-forming method. The effective adsorption capacity of micropores is much greater than that of mesopores. The combination of micropores and mesopores can achieve silicon adsorption and filling in micropores. Mesopores cannot be saturated with adsorption, so space is reserved. This technical solution can better alleviate the volume expansion of silicon during lithium intercalation. 3. Introducing silane gas in stages: The low concentration in the early stage of silicon infiltration can appropriately increase the adsorption capacity of mesopores for silane, and also fill some silicon in the mesopores to avoid physical barriers to silicon material, which would hinder lithium ion diffusion; The high concentration in the later stage accelerates the closure of the pores, reduces the specific surface area of ​​the material, and restricts the growth of silicon grains. 4. The novel silicon-carbon composite material based on graphite core prepared by this technical solution improves the rate performance and cycle stability of the anode material. The slower kinetics of the silicon-carbon material preferentially contact lithium ions and electrons before graphite particles, making the rate performance of each particle more similar. Compared with the traditional method of directly mixing CVD silicon-carbon material with graphite, it significantly improves the rate performance and cycle stability of the anode material. 5. The outermost porous polymer composite solid electrolyte layer has both high ionic conductivity and good flexibility. It can uniformly coat silicon carbon particles and has excellent structural stability. The use of solid electrolyte coating layer can effectively reduce electrolyte decomposition and improve its compatibility with electrolyte, thereby significantly improving the material's high temperature, fast charging and cycle stability. Attached Figure Description

[0025] Figure 1 This is a schematic diagram illustrating the preparation of a novel silicon-carbon composite material based on a graphite core. Detailed Implementation

[0026] The following specific embodiments are merely illustrative of the present invention and are not intended to limit the invention. After reading this specification, those skilled in the art can make modifications to these embodiments without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of the present invention.

[0027] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0028] Example 1

[0029] Graphite particles with a D50 of 8±1 μm and a phenolic resin coating agent were mixed uniformly. The mixture was placed in a carbonization furnace and heated to 600°C at a rate of 2°C / min under a nitrogen atmosphere, and held for 2 hours to obtain a graphite particle core-carbon shell structure. The precursor powder was mixed with a 30% potassium hydroxide aqueous solution and stirred for 5 hours, then washed until neutral and dried to remove moisture. Subsequently, the above material was placed in a tube furnace, and water vapor (the mass ratio of carbon shell to water vapor was 1:8) was added. The mixture was held at 950°C for 4 hours to activate and create pores, and then cooled to room temperature under a nitrogen atmosphere. The above composite material based on the graphite particle core and porous carbon shell was placed in a carbonization furnace and carbonized at 700°C for 2 hours to obtain the composite material based on the graphite particle core and porous carbon shell.

[0030] Example 2

[0031] Graphite particles with a D50 of 8±1 μm and asphalt coating agent were mixed uniformly. The mixture was placed in a carbonization furnace and heated to 600℃ at a rate of 2℃ / min under a nitrogen atmosphere, and held for 2 hours to obtain a graphite particle core-carbon shell structure. The precursor powder was mixed with a 30% potassium hydroxide aqueous solution and stirred for 6 hours, then washed until neutral and dried to remove moisture. Subsequently, the above material was placed in a tube furnace, and carbon dioxide (the mass ratio of carbon shell to carbon dioxide was 1:4) was added. The mixture was held at 850℃ for 5 hours to activate and create pores, and then cooled to room temperature under a nitrogen atmosphere. The above composite material based on graphite particle core and porous carbon shell was placed in a carbonization furnace and carbonized at 600℃ for 3 hours to obtain the composite material based on graphite particle core and porous carbon shell.

[0032] Example 3

[0033] Graphite particles with a D50 of 8±1 μm and a phenolic resin coating agent were mixed uniformly. The mixture was placed in a carbonization furnace and heated to 600°C at a rate of 2°C / min under a nitrogen atmosphere, and held for 2 hours to obtain a graphite particle core-carbon shell structure. The precursor powder was mixed with a 30% potassium hydroxide aqueous solution and stirred for 5 hours, then washed until neutral and dried to remove moisture. Subsequently, the above material was placed in a tube furnace, and carbon dioxide (the mass ratio of carbon shell to carbon dioxide was 1:4) was added. The mixture was held at 850°C for 5 hours to activate and create pores, and then cooled to room temperature under a nitrogen atmosphere. The above composite material based on graphite particle core and porous carbon shell was placed in a carbonization furnace and carbonized at 600°C for 3 hours to obtain the composite material based on graphite particle core and porous carbon shell.

[0034] Example 4

[0035] Graphite particles with a D50 of 8±1 μm and a phenolic resin coating agent were mixed uniformly. The mixture was placed in a carbonization furnace and heated to 600°C at a rate of 2°C / min under a nitrogen atmosphere, and held for 2 hours to obtain a graphite particle core-carbon shell structure. The material was then placed in a tube furnace, and steam (the mass ratio of carbon shell to steam was 1:3) was added. The furnace was held at 700°C for 8 hours to activate and create pores, and then cooled to room temperature under a nitrogen atmosphere. The composite material based on the graphite particle core and porous carbon shell was then carbonized in a carbonization furnace at 600°C for 2 hours to obtain the final composite material.

[0036] Example 5

[0037] Graphite particles with a D50 of 8±1 μm and coconut shell biomass coating agent were mixed evenly. The mixture was placed in a carbonization furnace and heated to 600℃ at a rate of 2℃ / min under a nitrogen atmosphere, and then held at this temperature for 2 hours to obtain a graphite particle core-carbon shell structure. Potassium hydroxide was added (the mass ratio of carbon shell to potassium hydroxide was 1:3), and the mixture was held at 800℃ for 2 hours to activate and create pores. The mixture was then cooled to room temperature under a nitrogen atmosphere and gradually washed with hydrochloric acid and water, followed by drying to obtain a composite material based on a graphite particle core and a porous carbon shell. The composite material based on the graphite particle core and porous carbon shell was then placed in a carbonization furnace and carbonized at 600℃ for 2 hours to obtain the final composite material based on a graphite particle core and a porous carbon shell.

[0038] Example 6

[0039] Graphite particles with a D50 of 8±1 μm and coconut shell biomass coating agent were mixed evenly. The mixture was placed in a carbonization furnace and heated to 600℃ at a rate of 2℃ / min under a nitrogen atmosphere, and then held for 2 hours to obtain a graphite particle core-carbon shell structure. The material was then placed in a tube furnace, and carbon dioxide (the mass ratio of carbon shell to carbon dioxide was 1:8) was added. The furnace was held at 900℃ for 5 hours to activate and create pores. The mixture was then cooled to room temperature under a nitrogen atmosphere to obtain a composite material based on a graphite particle core and a porous carbon shell. This composite material was then carbonized in a carbonization furnace at 600℃ for 2 hours to obtain the final composite material based on a graphite particle core and a porous carbon shell.

[0040] Example 7

[0041] Graphite particles with a D50 of 8±1 μm and an asphalt coating agent were mixed evenly. The mixture was placed in a carbonization furnace and heated to 600°C at a rate of 2°C / min under a nitrogen atmosphere, and then held for 2 hours to obtain a graphite particle core-carbon shell structure. The material was then placed in a tube furnace, and water vapor (the mass ratio of carbon shell to water vapor was 1:3) was added. The furnace was held at 700°C for 8 hours to activate and create pores, and then cooled to room temperature under a nitrogen atmosphere. The composite material based on the graphite particle core and porous carbon shell was then carbonized in a carbonization furnace at 600°C for 2 hours to obtain the final composite material.

[0042] Example 8

[0043] 1.0 kg of the composite material prepared in Example 1 was weighed and added to a fluidized bed. Nitrogen gas was introduced at a flow rate of 15 L / min, and the temperature was increased to 470°C at a rate of 5°C / min. Silane was then introduced at a flow rate of 13 L / min for nitrogen and 2 L / min for 30 min. The flow rate of silane was then reduced to 3 L / min and the flow rate of nitrogen to 12 L / min. The deposition time was 60 min. Subsequently, the flow rate of silane was reduced to 1 L / min and the flow rate of nitrogen to 14 L / min. After a deposition time of 30 min, the silane flow was stopped, and the nitrogen flow rate was restored to 15 L / min. The temperature was then increased to 590 °C at a rate of 5 °C / min, and acetylene was introduced at a flow rate of 1 L / min and a nitrogen flow rate of 14 L / min. After 30 min of this process, the acetylene flow rate was changed to 2 L / min and the nitrogen flow rate to 13 L / min. After a deposition time of 60 min, the acetylene flow was stopped, and the nitrogen flow rate was restored to 15 L / min. The material was then allowed to cool naturally to room temperature to obtain a single-carbon-coated CVD silicon-carbon / graphite anode material.

[0044] Polyamide was dissolved in N-methylpyrrolidone to obtain a polymer solution with a solid content of 2%; lithium lanthanum zirconium oxide was ultrasonically dispersed in water to obtain a lithium lanthanum titanium oxide dispersion with a solid content of 40%; the polymer solution and the lithium lanthanum zirconium oxide dispersion were mixed evenly, wherein the mass ratio of polyamide to lithium lanthanum zirconium oxide was 95:5; the prepared slurry was sprayed onto the surface of the above porous carbon-coated silicon carbon particles at a spraying temperature of 95°C; after drying, it was transferred to a 200°C oven for drying for 2 hours to obtain a novel silicon carbon composite material based on a graphite core.

[0045] Example 9

[0046] 1.0 kg of the composite material prepared in Example 2 was weighed and added to a fluidized bed. Nitrogen gas was introduced at a flow rate of 15 L / min, and the temperature was increased to 480°C at a rate of 5°C / min. Then, silane was introduced at a flow rate of 13 L / min for nitrogen and 2 L / min for 30 min. After that, the flow rate of silane was changed to 3 L / min and the flow rate of nitrogen was changed to 12 L / min. The deposition time was 60 min, after which the flow rate of silane was changed to 1 L / min and the flow rate of nitrogen was changed to 14 L / min. After a deposition time of 30 min, the silane flow was stopped, and the nitrogen flow rate was restored to 15 L / min. The temperature was then increased to 590 °C at a rate of 5 °C / min, and acetylene was introduced at a flow rate of 1 L / min and a nitrogen flow rate of 14 L / min. After 30 min of this process, the acetylene flow rate was changed to 2 L / min and the nitrogen flow rate to 13 L / min. After a deposition time of 60 min, the acetylene flow was stopped, and the nitrogen flow rate was restored to 15 L / min. The material was then allowed to cool naturally to room temperature to obtain a single-carbon-coated CVD silicon-carbon / graphite anode material.

[0047] Polyethylene oxide polymer was dissolved in water at 80°C to obtain a polymer solution with a solid content of 2%; lithium lanthanum titanium oxide was ultrasonically dispersed in water to obtain a lithium lanthanum titanium oxide dispersion with a solid content of 40%; the polymer solution and the lithium lanthanum titanium oxide dispersion were mixed evenly, wherein the mass ratio of polyethylene oxide polymer to lithium lanthanum titanium oxide was 40:60; the prepared slurry was sprayed onto the surface of the above porous carbon-coated silicon carbon particles at a spraying temperature of 95°C; after drying, it was transferred to an oven at 200°C and dried for 2 hours to obtain a novel silicon carbon composite material based on a graphite core.

[0048] Example 10

[0049] 1.0 kg of the composite material prepared in Example 3 was weighed and added to a fluidized bed. Nitrogen gas was introduced at a flow rate of 15 L / min, and the temperature was increased to 490°C at a rate of 5°C / min. Then, silane was introduced at a flow rate of 13 L / min for nitrogen and 1 L / min for 30 min. After that, the flow rate of silane was changed to 2 L / min and the flow rate of nitrogen was changed to 12 L / min. The deposition time was 90 min, after which the flow rate of silane was changed to 1 L / min and the flow rate of nitrogen was changed to 14 L / min. After a deposition time of 20 min, the silane flow was stopped, and the nitrogen flow rate was restored to 15 L / min. The temperature was then increased to 600 °C at a rate of 5 °C / min, and acetylene was introduced at a flow rate of 1 L / min and a nitrogen flow rate of 14 L / min. After 30 min of this process, the acetylene flow rate was changed to 2 L / min and the nitrogen flow rate to 13 L / min. After a deposition time of 60 min, the acetylene flow was stopped, and the nitrogen flow rate was restored to 15 L / min. The material was then allowed to cool naturally to room temperature to obtain a single-carbon-coated CVD silicon-carbon / graphite anode material.

[0050] Polymethyl methacrylate was dissolved in ethyl acetate to obtain a polymer solution with a solid content of 2%. Lithium lanthanum titanium oxide was ultrasonically dispersed in water to obtain a lithium lanthanum titanium oxide dispersion with a solid content of 40%. The polymer solution and the lithium lanthanum titanium oxide dispersion were mixed evenly, wherein the mass ratio of polymethyl methacrylate to lithium lanthanum titanium oxide was 60:40. The prepared slurry was sprayed onto the surface of the porous carbon-coated silicon carbon particles at a spraying temperature of 95°C. After drying, the particles were transferred to an oven at 200°C and dried for 2 hours to obtain a novel silicon carbon composite material based on a graphite core.

[0051] Example 11

[0052] 1.0 kg of the composite material prepared in Example 4 was weighed and added to a fluidized bed. Nitrogen gas was introduced at a flow rate of 15 L / min, and the temperature was increased to 470°C at a rate of 5°C / min. Then, silane was introduced at a flow rate of 13 L / min for nitrogen and 1 L / min for 120 min. After that, the flow rate of silane was increased to 2 L / min for nitrogen and 12 L / min for 30 min, after which the introduction of silane was stopped. The nitrogen flow rate was restored to 15 L / min, and the temperature was increased to 580 °C at a rate of 5 °C / min. Acetylene was then introduced at a flow rate of 1 L / min and a nitrogen flow rate of 14 L / min. After 30 min of this process, the acetylene flow rate was changed to 2 L / min and the nitrogen flow rate to 13 L / min. After 60 min of deposition, the acetylene flow was stopped, the nitrogen flow rate was restored to 15 L / min, and the material was allowed to cool naturally to room temperature to obtain a single-carbon-coated CVD silicon-carbon / graphite anode material.

[0053] Styrene-butadiene rubber was dissolved in acetone to obtain a polymer solution with a solid content of 3%; lithium phosphate was ultrasonically dispersed in water to obtain a lithium phosphate dispersion with a solid content of 35%; the polymer solution and the lithium phosphate dispersion were mixed evenly, wherein the mass ratio of styrene-butadiene rubber to lithium phosphate was 20:80; the prepared slurry was sprayed onto the surface of the porous carbon-coated silicon carbon particles at a spraying temperature of 100°C; after drying, it was transferred to a 300°C oven for drying for 1 hour to obtain a novel silicon carbon composite material based on a graphite core.

[0054] Example 12

[0055] 1.0 kg of the composite material prepared in Example 5 was weighed and added to a fluidized bed. Nitrogen gas was introduced at a flow rate of 15 L / min, and the temperature was increased to 480°C at a rate of 5°C / min. Then, silane was introduced at a flow rate of 14 L / min for nitrogen and 1 L / min for 90 min. After that, the flow rate of nitrogen was reduced to 13 L / min for nitrogen and 2 L / min for 60 min, and then the introduction of silane was stopped. The nitrogen flow rate was restored to 15 L / min, and the temperature was increased to 600 °C at a rate of 5 °C / min. Acetylene was then introduced at a flow rate of 1 L / min and a nitrogen flow rate of 14 L / min. After 30 min of this process, the acetylene flow rate was changed to 2 L / min and the nitrogen flow rate to 13 L / min. After 90 min of deposition, the acetylene flow was stopped, the nitrogen flow rate was restored to 15 L / min, and the material was allowed to cool naturally to room temperature to obtain a single-carbon-coated CVD silicon-carbon / graphite anode material.

[0056] Polyvinyl alcohol was dissolved in water at 80°C to obtain a polymer solution with a solid content of 2%; lithium aluminum germanium phosphate was ultrasonically dispersed in water to obtain a lithium aluminum germanium phosphate dispersion with a solid content of 40%; the polymer solution and the lithium aluminum germanium phosphate dispersion were mixed evenly, wherein the mass ratio of polyvinyl alcohol to lithium aluminum germanium phosphate was 20:80; the prepared slurry was sprayed onto the surface of the porous carbon-coated silicon carbon particles at a spraying temperature of 95°C; after drying, it was transferred to a 300°C oven for drying for 2 hours to obtain a novel silicon carbon composite material based on a graphite core.

[0057] Example 13

[0058] 1.0 kg of the composite material prepared in Example 6 was weighed and added to a fluidized bed. Nitrogen gas was introduced at a flow rate of 15 L / min, and the temperature was increased to 470°C at a rate of 5°C / min. Then, silane was introduced at a flow rate of 14 L / min for nitrogen and 1 L / min for 90 min. After this time, the flow rate was reduced to 13 L / min for nitrogen and 2 L / min for 90 min, and then the introduction of silane was stopped. The nitrogen flow rate was restored to 15 L / min, and the temperature was increased to 580 °C at a rate of 5 °C / min. Acetylene was then introduced at a flow rate of 1 L / min and a nitrogen flow rate of 14 L / min. After 30 min of this process, the acetylene flow rate was changed to 2 L / min and the nitrogen flow rate to 13 L / min. After 70 min of deposition, the acetylene flow was stopped, the nitrogen flow rate was restored to 15 L / min, and the material was allowed to cool naturally to room temperature, thus obtaining a single-carbon-coated CVD silicon-carbon / graphite anode material.

[0059] Phenolic resin was dissolved in water at 80°C to obtain a polymer solution with a solid content of 1%; lithium phosphorus oxygen nitrogen was ultrasonically dispersed in water to obtain a lithium phosphorus oxygen nitrogen dispersion with a solid content of 45%; the polymer solution and the lithium phosphorus oxygen nitrogen dispersion were mixed evenly, wherein the mass ratio of phenolic resin to lithium phosphorus oxygen nitrogen was 90:10; the prepared slurry was sprayed onto the surface of the above porous carbon-coated silicon carbon particles at a spraying temperature of 95°C; after drying, it was transferred to an oven at 150°C and dried for 3 hours to obtain a novel silicon carbon composite material based on a graphite core.

[0060] Example 14

[0061] 1.0 kg of the composite material prepared in Example 7 was weighed and added to a fluidized bed. Nitrogen gas was introduced at a flow rate of 15 L / min, and the temperature was increased to 480°C at a rate of 5°C / min. Then, silane was introduced at a flow rate of 14 L / min for nitrogen and 1 L / min for 60 min. After that, the flow rate was increased to 13 L / min for nitrogen and 2 L / min for 70 min, and then the introduction of silane was stopped. The nitrogen flow rate was restored to 15 L / min, and the temperature was increased to 580 °C at a rate of 5 °C / min. Acetylene was then introduced at a flow rate of 1 L / min and a nitrogen flow rate of 14 L / min. After 30 min of this process, the acetylene flow rate was changed to 2 L / min and the nitrogen flow rate to 13 L / min. After 90 min of deposition, the acetylene flow was stopped, the nitrogen flow rate was restored to 15 L / min, and the material was allowed to cool naturally to room temperature to obtain a single-carbon-coated CVD silicon-carbon / graphite anode material.

[0062] Polyurethane was dissolved in N-methylpyrrolidone to obtain a polymer solution with a solid content of 1%; lithium lanthanum titanium oxide was ultrasonically dispersed in water to obtain a lithium lanthanum titanium oxide dispersion with a solid content of 45%; the polymer solution and the lithium lanthanum titanium oxide dispersion were mixed evenly, wherein the mass ratio of polyurethane to lithium lanthanum titanium oxide was 82:15; the prepared slurry was sprayed onto the surface of the above porous carbon-coated silicon carbon particles at a spraying temperature of 95°C; after drying, it was transferred to a 200°C oven for drying for 3 hours to obtain a novel silicon carbon composite material based on a graphite core.

[0063] Comparative Example 1 Phenolic resin was placed in a carbonization furnace and heated to 500°C at a rate of 2°C / min under a nitrogen atmosphere, then held at that temperature for 2 hours to obtain a graphite particle core-carbon shell structure. The material was then placed in a tube furnace, and water vapor (the mass ratio of carbon shell to water vapor was 1:8) was added. The furnace was held at 900°C for 8 hours to activate and create pores. The mixture was then cooled to room temperature under a nitrogen atmosphere to obtain a composite material based on a graphite particle core and a porous carbon shell.

[0064] 1.0 kg of porous carbon was weighed and added to a fluidized bed. Nitrogen gas was introduced at a flow rate of 15 L / min, and the temperature was increased to 470 °C at a rate of 5 °C / min. Then, silane was introduced at a flow rate of 13 L / min for nitrogen and 2 L / min for 60 min. Afterward, the silane flow rate was changed to 3 L / min and the nitrogen flow rate to 12 L / min, with a deposition time of 120 min. Subsequently, the silane flow rate was changed to 1 L / min and the nitrogen flow rate to 14 L / min, with a deposition time of [missing information]. After 60 minutes, the silane flow was stopped, and the nitrogen flow rate was restored to 15 L / min. The temperature was then increased to 590 °C at a rate of 5 °C / min. Acetylene was then introduced at a flow rate of 1 L / min and the nitrogen flow rate was 14 L / min. After 30 minutes, the acetylene flow rate was changed to 2 L / min and the nitrogen flow rate was 13 L / min. After 60 minutes of deposition, the acetylene flow was stopped, and the nitrogen flow rate was restored to 15 L / min. The material was then allowed to cool naturally to room temperature to obtain a single-carbon-coated CVD silicon-carbon / graphite anode material.

[0065] Polyamide was dissolved in N-methylpyrrolidone to obtain a polymer solution with a solid content of 2%; lithium lanthanum zirconium oxide was ultrasonically dispersed in water to obtain a lithium lanthanum titanium oxide dispersion with a solid content of 40%; the polymer solution and the lithium lanthanum zirconium oxide dispersion were mixed evenly, wherein the mass ratio of polyamide to lithium lanthanum zirconium oxide was 95:5; the prepared slurry was sprayed onto the surface of the above-mentioned primary carbon-coated CVD silicon-carbon / graphite anode material particles at a spraying temperature of 95°C; after drying, it was transferred to a 200°C oven for drying for 2 hours to obtain a novel silicon-carbon composite material based on a graphite core.

[0066] The above-mentioned silicon-carbon material was mixed evenly with graphite with a D50 of 8±1μm to obtain the CVD silicon-carbon / graphite anode material. The specific capacity of the anode material prepared at this time was similar to that of Example 8.

[0067] Comparative Example 2 Graphite particles with a D50 of 8±1 μm and a phenolic resin coating agent were mixed uniformly. The mixture was placed in a carbonization furnace and heated to 600°C at a rate of 2°C / min under a nitrogen atmosphere, and then held at that temperature for 2 hours to obtain a graphite particle core-carbon shell structure. Subsequently, the above material was placed in a tube furnace, and water vapor (the mass ratio of carbon shell to water vapor was 1:8) was added. The furnace was then held at 900°C for 8 hours to activate and create pores. After cooling to room temperature under a nitrogen atmosphere, a composite material based on a graphite particle core and a porous carbon shell was obtained.

[0068] 1.0 kg of the prepared composite material was weighed and added to a fluidized bed. Nitrogen gas was introduced at a flow rate of 15 L / min, and the temperature was increased to 470 °C at a rate of 5 °C / min. Silane was then introduced at a flow rate of 13 L / min for nitrogen and 2 L / min for 30 min. After this time, the silane flow rate was changed to 3 L / min and the nitrogen flow rate to 12 L / min. The deposition time was 60 min, after which the silane flow rate was changed to 1 L / min and the nitrogen flow rate to 14 L / min. After a deposition time of 30 min, the silane flow was stopped, and the nitrogen flow rate was restored to 15 L / min. The temperature was then increased to 590 °C at a rate of 5 °C / min. Acetylene was then introduced at a flow rate of 1 L / min and the nitrogen flow rate was 14 L / min. After 30 min of this process, the acetylene flow rate was changed to 2 L / min and the nitrogen flow rate to 13 L / min. After a deposition time of 60 min, the acetylene flow was stopped, and the nitrogen flow rate was restored to 15 L / min. The material was then allowed to cool naturally to room temperature, yielding a single-carbon-coated CVD silicon-carbon / graphite anode material.

[0069] Comparative Example 3 Graphite particles with a D50 of 8±1 μm and a phenolic resin coating agent were mixed uniformly. The mixture was placed in a carbonization furnace and heated to 600°C at a rate of 2°C / min under a nitrogen atmosphere, and then held at that temperature for 2 hours to obtain a graphite particle core-carbon shell structure. Subsequently, the above material was placed in a tube furnace, and water vapor (the mass ratio of carbon shell to water vapor was 1:8) was added. The furnace was then held at 900°C for 8 hours to activate and create pores. After cooling to room temperature under a nitrogen atmosphere, a composite material based on a graphite particle core and a porous carbon shell was obtained.

[0070] 1.0 kg of the prepared composite material was weighed and added to a fluidized bed. Nitrogen gas was introduced at a flow rate of 15 L / min, and the temperature was increased to 470 °C at a rate of 5 °C / min. Then, silane was introduced at a flow rate of 13 L / min for nitrogen and 2 L / min for 120 min. After deposition, the silane was stopped, and the nitrogen flow rate was restored to 15 L / min. The temperature was then increased to 590 °C at a rate of 5 °C / min. Acetylene was then introduced at a flow rate of 2 L / min for nitrogen and 13 L / min for 60 min. After deposition, the acetylene was stopped, and the nitrogen flow rate was restored to 15 L / min. The material was then allowed to cool naturally to room temperature to obtain a single-carbon-coated CVD silicon-carbon / graphite anode material.

[0071] Polyamide was dissolved in N-methylpyrrolidone to obtain a polymer solution with a solid content of 2%; lithium lanthanum zirconium oxide was ultrasonically dispersed in water to obtain a lithium lanthanum titanium oxide dispersion with a solid content of 40%; the polymer solution and the lithium lanthanum zirconium oxide dispersion were mixed evenly, wherein the mass ratio of polyamide to lithium lanthanum zirconium oxide was 95:5; the prepared slurry was sprayed onto the surface of the above porous carbon-coated silicon carbon particles at a spraying temperature of 95°C; after drying, it was transferred to a 200°C oven for drying for 2 hours to obtain a novel silicon carbon composite material based on a graphite core.

[0072] Performance testing

[0073] The materials prepared in Examples 1-7 were tested for specific gravity and pore size on Bestech testing equipment.

[0074] The negative electrode materials prepared in the above embodiments and comparative examples were assembled into batteries, and their relevant performance was tested. The specific steps included: (1) Electrode preparation: Weigh the required material mass of the silicon-carbon material prepared in the examples and comparative examples according to the formula ratio (SiC:CMC:SBR:SP=95:2:1.5:1.5). Weigh a certain amount of CMC and deionized water in a beaker according to the solid content of 30%-50%. Stir until the CMC is completely dissolved and the solution is transparent and viscous. At this time, add conductive agent SP and stir for 90 min. Then weigh the active material and transfer it to the above viscous solution. Continue stirring for 60 min. Finally, add emulsion SBR and stir for about 30 min. Then coat it on the current collector and dry at 80°C.

[0075] (2) Button cell assembly: The dried electrode sheets are filled with a punching machine to obtain electrode sheets with a diameter of 12 mm. Lithium sheet is used as the counter electrode. 1 M lithium hexafluorophosphate is dissolved in a mixed solution of ethylene carbonate and diethyl carbonate with a volume ratio of 1:1. 5% fluoroethylene ester is added as electrolyte. A 20 μm separator is used in the assembly process to assemble CR2032 button cells.

[0076] (3) Test conditions: Charge and discharge test at 0.1C rate, cutoff voltage set at 0.005V-2V.

[0077] The test results are shown in Tables 1 and 2. Table 1 shows the comparative data for Examples 1-7. Table 2 shows the electrochemical data for Examples 8-14 and Comparative Examples 1-3.

[0078] Table 1. Summary of comparison data for Examples 1-7

[0079] Table 2. Electrochemical data analysis of Examples 8-14 and Comparative Examples 1-3

[0080] Based on the above experiments and data, we can conclude that: 1. A comparison of the specific surface area and pore structure data of Examples 1-7 shows that the chemical and physical activation methods can better control the pore structure of the material, and the material with high microporosity has a relatively higher specific surface area.

[0081] 2. Comparing Examples 8-14 and Comparative Examples 1-3, under conditions of similar battery specific capacity, the anode material with a special structure prepared by the method of the present invention (graphite particles as the core, porous carbon as the outer shell, CVD deposited silicon carbon, followed by sequential coating of a carbon layer and a polymer composite solid electrolyte layer on the silicon carbon material with a specific structure) exhibits superior initial coulombic efficiency and capacity retention of lithium-ion batteries compared to the traditional anode material prepared by directly mixing porous carbon-based CVD silicon carbon and graphite. This demonstrates that the anode material prepared by the method of the present invention can significantly improve the cycle life and rate performance of lithium-ion batteries, which is of great significance to the development of lithium-ion batteries.

Claims

1. A method for preparing a novel silicon-carbon composite material based on a graphite core, characterized in that... Includes the following steps: S1. Graphite and coating agent are mixed evenly and dried to obtain the first mixture; S2. The first mixture is placed in a carbonization furnace and pre-carbonized under a nitrogen atmosphere to obtain a graphite particle core-carbon shell structure. A pore-forming agent is added and the mixture is heated to activate and form pores. The mixture is then cooled to room temperature under a nitrogen atmosphere to obtain a composite material based on a graphite particle core and a porous carbon shell, wherein the microporosity is 40-85%, the mesoporosity is 10-30%, and the mesopore size is 2-5 nm. S3. The above-mentioned composite material based on graphite particle core and porous carbon shell is placed in a carbonization furnace for carbonization to obtain a carrier. S4. Weigh a certain mass of the carrier and put it into the fluidized bed, introduce nitrogen gas, raise the temperature, introduce silane in stages, stop introducing silane after the deposition is completed, raise the temperature again, introduce acetylene, stop introducing acetylene after the coating is completed, and cool naturally to room temperature to obtain a CVD silicon-carbon / graphite anode material with one carbon coating. S5. Add the solid electrolyte to the polymer aqueous solution and disperse it evenly to obtain a slurry; S6. Spray the slurry onto the surface of the CVD silicon-carbon / graphite anode material with primary carbon coating prepared above, and then dry it to obtain a novel silicon-carbon composite material based on a graphite core.

2. The method for preparing a novel silicon-carbon composite material based on a graphite core according to claim 1, characterized in that, Includes the following steps: S1. Mix graphite and coating agent evenly and dry, wherein the coating agent accounts for 60% of the total mass of graphite particles and coating agent; S2. The mixture is placed in a carbonization furnace and pre-carbonized at 600℃ for 2 hours under a nitrogen atmosphere at a rate of 2℃ / min to obtain a graphite particle core-carbon shell structure. A pore-forming agent is added according to calculations, and the mixture is kept at 700~950℃ for 1~3 hours to activate and form pores. The mixture is then cooled to room temperature under a nitrogen atmosphere to obtain a composite material based on a graphite particle core and a porous carbon shell, wherein the microporosity is 40-85%, the mesoporosity is 10-30%, and the mesopore size is 2-5nm. S3. The above composite material based on graphite particle core and porous carbon shell is placed in a carbonization furnace and carbonized at 500~700℃ for 1~3h to obtain a carrier; S4. Weigh a certain mass of the carrier and put it into the fluidized bed. Introduce nitrogen gas and heat it to 450~490℃ at a rate of 5℃ / min. Introduce a certain amount of silane in stages (the density is calculated as 1.44g / L, and the decomposition rate of silane in this temperature range is calculated as 90%). After the deposition is completed, stop introducing silane. Heat it to 570~600℃ at a rate of 5℃ / min. Introduce acetylene according to the coating amount of 2~5%. After the coating is completed, stop introducing acetylene and let it cool naturally to room temperature to obtain a single carbon-coated CVD silicon-carbon / graphite anode material. S5. Add the solid electrolyte to the polymer aqueous solution and disperse it evenly to obtain a slurry; S6. Spray the slurry onto the surface of the CVD silicon-carbon / graphite anode material with primary carbon coating prepared above, and then dry it to obtain a novel silicon-carbon composite material based on a graphite core.

3. The method for preparing a novel silicon-carbon composite material based on a graphite core according to claim 2, characterized in that, In step S1, the graphite D50 is 8±1μm; the coating agent includes phenolic resin, asphalt or coconut shell-based biomass carbon; wherein the coating agent accounts for 60% of the total mass of the graphite particles and the coating agent.

4. The method for preparing a novel silicon-carbon composite material based on a graphite core according to claim 2, characterized in that, In step S2, the pore-forming agent is one or two of water vapor, carbon dioxide, or potassium hydroxide; the pre-carbonization temperature is 300-500℃, and the pre-carbonization time is 2-3 hours; the activation temperature is 700-950℃, and the activation time is 3-8 hours; the specific surface area of ​​the composite material is 1400-2100 m². 2 / g, total pore volume is 0.74-1.1cm³ 3 / g, microporosity 40-85%, mesoporosity 10-30%, average pore size 1.8-2.4nm.

5. The method for preparing a novel silicon-carbon composite material based on a graphite core according to claim 2, characterized in that, In step S3, the carbonization temperature is 500~700℃ and the carbonization time is 1~3h.

6. The method for preparing a novel silicon-carbon composite material based on a graphite core according to claim 2, characterized in that, In step S4, the silane deposition temperature is 460~490℃, the total amount of nitrogen carrier gas and silane gas introduced is 15L / min, and the concentration of silane introduced in stages is 5~20%; the primary coating temperature is 570~600℃, the total amount of nitrogen carrier gas and acetylene gas introduced is 15L / min, and the acetylene concentration introduced is 5~15% based on the coating amount of 2~5%.

7. The method for preparing a novel silicon-carbon composite material based on a graphite core according to claim 2, characterized in that, In step S5, the solid electrolyte is selected from at least one of lithium lanthanum titanium oxide, lithium aluminum titanium phosphate, lithium aluminum germanium phosphate, lithium lanthanum zirconium oxide, lithium germanium phosphorus sulfide, lithium phosphorus oxy nitrogen, or lithium phosphate; the polymer is selected from at least one of phenolic resin, acrylamide, polyethylene, polystyrene, polyvinyl alcohol, polyvinyl chloride, polyether, polyester, polyamide, polyurethane, polysulfide rubber, polymethyl methacrylate, or styrene-butadiene rubber; the solid content of the polymer aqueous solution is 1-3%; the solid content of the slurry is 30%-45%; the mass ratio of the polymer to the solid electrolyte is (10%-85%):(90%-15%), and the sum of the masses of the polymer and the solid electrolyte is 100%.

8. The method for preparing a novel silicon-carbon composite material based on a graphite core according to claim 2, characterized in that, In step S6, the spray temperature is 90℃~100℃; the drying temperature is 150℃~300℃, and the drying time is 0.5h~4h.

9. An application of a novel silicon-carbon composite material based on a graphite core, characterized in that, This includes its use as a negative electrode material in the preparation of lithium-ion batteries.

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